1. Field of the Invention
The invention concerns an electric toothbrush which operates a brushhead with three dimensional stroke movement.
2. The Related Art
Electric toothbrushes have been in development for over sixty years. The earliest type were relatively simple, electro-mechanical versions of manual toothbrushes with limited back-and-forth movement. More recent developments have featured enhanced performance batteries and high efficiency miniaturized electric motors. Today battery powdered electric toothbrushes figure prominently in the general product classification.
Yet with these drive train improvements, the basic electro-mechanical arrangement differs little from the earliest devices marketed. Essentially, the typical product consists of a battery, either rechargeable or replaceable, adjacent end to end to a small high speed electric motor. A drive shaft operated by the motor may in turn either be coupled to a mechanical drive train with reduction gears or crank arms or may be coupled with simple direct drive.
Most mechanical designs involve an oscillating fixed bristle array brush operating with a narrow back and forth angular range of rotary motion. Travel is essentially in a two dimensional plane. Various types of mechanical devices such as gears with levers, in combination or separately, deliver the rotary motion. In some instances, the brushhead may feature individually rotatable brush bundles driven by gearing alone. A third category of electric brush incorporates ultrasonic technology, either alone or in combination with an oscillating brush.
Among the considerable volume of literature is U.S. Pat. No. 5,577,285 (Drossler) which describes an electric toothbrush in which a rotary shaft translates to a bristle supporting structure an alternating or a rotary motion. U.S. Pat. No. 5,467,494 (Muller et al.) describes a mechanism with a pair of mutually pivotable parts, the first serving as a handle and the second a brushhead. A spring arranged between the parts snaps when a given pressure threshold is exceeded and resumes its original position when the pressure is decreased. Angular rotation is imparted by the spring action. U.S. Pat. No. 4,276,672 (Teague, Jr. et al.) reports a water powered nutating system effectuating a rotary motion which in turn converts to an orbital motion in the brush working element. U.S. Pat. No. 3,538,530 (Stemme) provides a motor-driven toothbrush based on a guide arrangement with cam faces with an outline resembling a figure eight. The guide shifts that portion of a brush stem extending into the housing. Thereby the entire brush operates along a path resembling the figure eight. U.S. Pat. No. 5,177,826 (Vrignaud et al.) reports a pair of disc-like rotary brushes mounted for rotation about an axis generally perpendicular to a length of the handle. Between the rotary pair are upper and lower linear brushes rotating in a linear reciprocating motion generally perpendicular to the axis. A cylindrical cam element mounted for eccentric rotation operates as part of the system. A further gear is secured to the cam element, but mounted for concentric rotation. U.S. Pat. No. 5,077,855 (Ambasz) describes an electric toothbrush including a drive unit having a motor and a transmission that simultaneously drive a shaft and a brushhead extension reciprocably in a direction parallel to the axis of the shaft. A brush unit includes a brushhead coupled to the extension for lengthwise reciprocating motion on which several bristle holders, each carrying several bristle tufts, are mounted individually for pivotal movement about an axis spaced apart from and parallel to the drive shaft. A crank coupled to the drive shaft imparts pivotable movement to each bristle holder individually.
Even with the options and improvements categorized above, most of the mechanical designs remain complex. Many small parts are required to impart a rotary motion to the bristles or head. Furthermore, the necessarily miniature character of these parts and their unsealed arrangement accelerates wear in the abrasive environment typical of the oral cavity.
Another significant problem is that of efficacy. Electric toothbrushes when compared to the manual variety are not more efficient. For instance, little difference has been seen in their respective tartar removal performance.
Still another major shortcoming of the known art is its non-conformance to best practice toothbrush movement. Most periodontology graduate program textbooks promote the Bass technique. It is recommended for bacterial plaque removal adjacent to and directly beneath the gingival margin. This area is the most significant in the control of gingival and periodontal disease. Elements of the Bass technique include positioning the brush along the gum line at a 45xc2x0 angle. One row of the bristles should be nestled slightly under the gums where they meet the teeth. Thereafter the brush is gently wiggled back and forth ten times to loosen plaque within the hidden fold along the gum line. In a final step, the brush is lifted away and repositioned to perform the same motion with the next set of teeth and gums.
Accordingly, it is an object of the present invention to provide an electric toothbrush delivering three dimensional motion to the bristles.
It is another object of the present invention to provide an electric toothbrush delivering a three dimensional motion which conforms to the Bass technique for bacterial plaque removal adjacent to and directly beneath the gingival margin.
Still a further object of the present invention is to provide an electric toothbrush of simpler mechanical design and which permits less costly replacement of brushheads than those normally associated with mechanical drive systems presently in commerce.
These and other objects of the present invention will become more readily apparent through the following summary and detailed description.
An electric toothbrush is provided which includes:
(i) an elongate body defining a handle and having an interior cavity formed therein, the cavity extending from a front to a rear end;
(ii) a power source mounted within the cavity;
(iii) an elongate drive shaft aligned from front to rear end driven rotatably by the power source;
(iv) a camwheel mounted on the drive shaft;
(v) a yoke with projecting arms, the camwheel axially reciprocating between the projecting arms thereby imparting a reciprocating movement to the drive shaft;
(vi) a crankshaft section axially downstream from the yoke and being driven by the drive shaft;
(vii) an output shaft axially aligned with the drive shaft; and
(viii) a collar with a guide track eccentrically coupling the crankshaft section to the output shaft thereby imparting both lateral and reciprocating rotary motion to the output shaft.
The mechanical drive system embraces within-a closed housing a completely self contained three dimensional system. No mechanical drive aspects are required external to the brush handle housing in order to provide a brushing action.
A simple brushhead is positioned telescopically onto the output shaft. Retention is best achieved by a detent. No moving parts are necessary in the brushhead and it can be formed from a short, hollow shaft.
The combined lateral and reciprocating rotary movement of the output shaft is transmitted to the brushhead. Each individual brush tip fiber of the brushhead is caused to move clockwise in a predicable oval pattern. The fiber tips move in concert to create an overlapping scrubbing pattern. Travel of the brush tips are conducive to improved cleaning of tooth interstices and gum lines in a manner suggested by the Bass technique.
Advantageously the camwheel is canted between 1 and 20xc2x0 relative to the drive shaft. More preferably the cant ranges from 4 to 10xc2x0.
The output shaft downstream from the collar has a flexible section adjacent the front end of the elongate body. Bending can occur along that section at an angle between 1 and 40xc2x0.